The sequencing of an ever increasing number of eukaryotic genomes of model and non-model organisms, including the recent completion of the first human genome, is providing a rapidly expanding pipeline of probable genes, many of which have as yet only a putative biological function ascribed to them on the basis of sequence similarity with known genes. Even where the biological function is known, it is becoming clear that the genome holds an extraordinary amount of as yet ill-understood regulatory information as to the temporal and spatial expression of these genes to provide for the exquisite cellular and tissue architectures common while unique to all organisms. This is surely an exhilarating reminder that much of the natural world remains to be explored at the molecular level. DNA microarrays provide a natural vehicle for this exploration. Comprehensive genome-wide surveys of gene expression patterns or function are now possible in a large number of organisms including humans, often at the level of individual cell type or tissue. The results can be viewed as maps that reflect the order and logic of the genetic program, rather than the physical order of genes on chromosomes. Increasingly, a temporal component is being added to many microarray studies to provide a dynamic view of the world within the cell. Furthermore, the molecular pathology of diseases such as cancer and bacterial or viral infection is now open to analysis by DNA microarray analysis and complementary technologies. Research using DNA microarrays and other genome-scale technologies should also help to rapidly accelerate our knowledge of gene function and molecular biology between the model organisms and other species. In this eight-day laboratory and lecture course, students will learn how to troubleshoot the array-making equipment, prepare DNA microarrays from a variety of sources, perform hybridization experiments using the prepared arrays, and learn in detail how to analyze and present data arising from these experiments. It should be emphasized that more and more emphasis will be placed on the data handling and analysis aspects of this field as the technology matures. The goal of the course is to train students so that they can return to their own laboratories and immediately apply this powerful technology in their own research.